LEASES - Cost and Accumulated Depreciation (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Operating Leased Assets [Line Items]
Property and equipment, at cost	$ 2,906,648	$ 2,843,690
Less: accumulated depreciation	(1,408,601)	(1,323,003)
Property and equipment, net	1,498,047	$ 1,520,687
Mohegan Sun
Operating Leased Assets [Line Items]
Property and equipment, at cost	484,143
Less: accumulated depreciation	(198,080)
Property and equipment, net	$ 286,063